I, too, let my cats outside. Shadow, a Manx X and Calli - a Calico - both neutered - love it outdoors. We have a HUGE Red Cedar tree in the back yard that they both love to climb. They both use a piece of driftwood in the back yard as a scratching post and watching them chase grasshoppers is a hoot. I tried the indoor thing but both (from the local SPCA) must have been outdoor cats because when kept indoors the noise is unbearable! Shadow particularly will howl and will scratch the door and rugs to get out. Both will come when I call them in, thank goodness! I do believe that they are better outdoors where they can run in the grass and sleep under the plants and chase grasshoppers...